The traditional non-electrolytic methods of breaking down and removing ammonia and ammonium from water have basically involved engineering a system which exposes the water to oxygen. The oxidation reactions are promoted, which usually have had a high aerobic micro-biological component. However, such oxidation reactions predominantly leave the nitrogen in the form of (dissolved) nitrate and of the various (gaseous) oxides of nitrogen. These nitrogen compounds themselves can be health hazards, and should not be simply discharged into the environment, at least not in the large quantities that arise from treating waste-water.
Patent publication U.S. Pat. No. 6,083,377 (Lin+Shelp, July 2000) describes the use of electrolysis, in effecting the direct breakdown of ammonium to nitrogen gas. Effective though it can be, under many conditions, the disclosed electrolysis technology works best when the concentration of ammonium is high. When the concentration is low, the amount of electrical energy needed to drive current through the electrolytic cells can spoil the economics of the process. If the energy usage is kept economical, the ammonium content of the discharged water, though diminished, still might be too high.
It is an aim of the present invention to provide (a) that the ammonium in waste-water is converted, by electrolysis, directly to nitrogen gas; (b) that the concentration level of ammonia and ammonium in the discharged water is acceptably low; and yet (c) that only an economic amount of electrical energy is required.
Breaking down ammonium by electrolysis, when properly engineered and operated, avoids the formation of the unwanted and toxic oxidation products. Also, it is recognised that electrolytic treatment is much less dependent on ambient temperature than aerobic micro-biological oxidation. That is to say, electrolysis is a preferred method, especially in cold climates, for achieving the required diminishment of ammonium, if it could be done more economically.